Elastin obtained from the lungs of cockerals, rats, rabbits and the rhesus monkey will be compared after isolation and characterization. Both soluble and isoluble forms of elastin will be studied. Soluble forms of elastin will be obtained by first retarding intra- and intermolecular crosslinking either by nutritional copper-deficiency or lathyrism. The tests for the degree of homology between various elastins will be based on amino acid composition electrophoretic mobility using acrylamide gel, chromatographic behavior, peptide mapping, immunochemical properties, and when possible N-terminal amino acid sequence data. A comparison between elastins isolated from various locations in the lung to arterial elastin will also be made. The primary purpose of the investigation is to provide basic information on the properties of lung elastin so that basic studies on lung elastin metabolism will be made more feasible.